Our invention relates to an apparatus for data transfer with a disklike record medium such as, typically, a flexible magnetic disk commonly known as a floppy disk. More particularly, our invention deals with such an apparatus including a floppy disk drive (FDD) under the control of host equipment normally comprising a central processor unit (CPU) and an FDD controller.
As is well known, the FDD is not a self contained unit; rather, one FDD or a set of FDDs are coupled to, and controlled by, host equipment to make up a data processing system. Normally, each FDD has no power switch of its own but is electrically turned on and off by a power switch provided to the host equipment. When the host equipment is switched on, therefore, so is the FDD, even though the latter may not actually perform the data transfer function for which it is intended during all the period when the system power switch is held closed. This of course incurs a substantial waste of power.
Prior art attempts at reducing such waste of power in FDDs are seen in U.S. patent applications Ser. Nos. 634,318, now abandoned, and 634,320, both filed July 25, 1984, and Ser. No. 642,050, filed Aug. 17, 1984, all by Tsuyuguchi et al. and assigned to the assignee of our present application. All these prior applications suggest to automatically switch off supply lines to some components of the FDD when their operations are not required, while the system power switch is held closed. Although these conventional solutions are satisfactory in their own ways, we believe that the saving of power should not sacrifice the response of the FDD, that is, the immediate commencement of data transfer in response to a command from the host equipment.